In some cases, vertical forming machines and/or installations are used for unit packaging or for bulk packaging of products. Inclined packaging machines for packaging fragile products are also known. In other cases, horizontal packaging machines are used; said machines can be very fast because unlike what occurs in vertical or inclined systems, the travelling speed of the product in horizontal packaging systems does not depend on gravity.
In the aforementioned machines, a film tube is obtained from a film that is sealed longitudinally; said tube is then separated into individual packages with a product contained therein by means of transverse sealing and cutting. Generally, one end of a package is closed (the other end is closed by the previous cutting/sealing operation), one end of a new package is sealed and a cut is made between both ends in one and the same operation, a package closed at both ends and a new film tube closed at one end being obtained.
In a horizontal packaging machine the obtained film tube is horizontal and is supported by transport means such as a conveyor belt. When the product to be packaged is introduced in the film tube, said product is supported on the conveying means during the rest of the packaging process. In contrast, in a vertical packaging machine the obtained film tube is vertical, and when the product to be packaged is introduced in the film tube it falls inside the film tube due to gravity. The product is then supported by the film tube itself during the rest of the packaging process, in particular it is supported by the closed end of the film tube, and additional safety measures have to be taken into account for preventing the film tube from being accidentally broken due to the weight of the product. Therefore, a vertical packaging machine faces problems not present in a horizontal packaging machine, and said problems remains when the products must be vacuum packaged, in addition to the difficulty in applying the vacuum in a film tube. For this reason, the film tube is generally formed in the vertical machine, and once the product is introduced in the film tube closed at one end, said portion of film tube closed at one end with the product contained therein is separated from the rest of the film tube for subsequently applying the vacuum and sealing the package in a subsequent process in another station of the machine, or in a different machine designed for that purpose.
Application EP2296974A1 discloses a vacuum packaging station that receives a bag (or a package) open at one of its ends with the product contained therein, and then extracts gas from inside the bag and seals the bag to obtain a package after correctly positioning the bag.
Document U.S. Pat. No. 3,958,391A1 also discloses an apparatus for vacuum packaging products. The apparatus receives a bag (or a package) open at one of its ends with the product contained therein.
Application WO2010/018239A1 belonging to the applicant discloses a vertical packaging machine comprising a forming tube, film feeding means suitable for applying a film on the forming tube, longitudinal film sealing means, first transverse film sealing means to form an upper closure seal and a lower closure seal, and a chamber configured for internally housing a portion of the film tube separated from the rest of the film tube and extracting the air contained in said portion. The first transverse film sealing means produces an upper closure seal with an opening, and the chamber comprises seconds sealing means suitable for sealing the opening once the air is extracted from inside the portion through said opening in the chamber.
Application EP2500286A1 discloses a vacuum forming apparatus comprising a first vacuum space member and a second vacuum space member disposed on opposite sides of the film tube. Both vacuum space members cooperate with each other to generate an inner space where the film tube is cut, the gas from the inside of the tube being evacuated through said cut.